Ascenders are mechanical devices which will allow a rope or the like to move in only one direction. Ascenders are used in a wide range of applications such as personal fall protection, in rock climbing using the rope for an ascending maneuver, hauling systems, pulley safety locks, and rope cleats. Ascenders will grip on any type of rope--kernmantle, twisted, braided, or plated.
Two basic types of ascenders are generally known. They are first a toothed cam type. Commercial manufactures of the toothed cam type include Jumar, CMI, and Petzl. These devices have slanted spike-like teeth. They are the most common type of ascender found in ascending systems. These devices usually can be put on or off the rope with one hand. One drawback is the tendency for mud or ice to clog the teeth. Once the teeth are clogged, the device fails. Most toothed style ascenders are right and left handed, and as a rule are sold in pairs.
A second basic type of ascender is a ridged cam. They have fewer, but larger, rounded ridges perpendicular to the direction of travel. No concavity of the bite surface is used. A pair of these are often used on sailboats. This simple, yet elegant design, presses or squeezes the rope with ridges instead of spike teeth. This design grabs wet, icy, or muddy ropes more securely than will a toothed cam, however, this will be at the expense of rope damage. Most ridged cam ascenders require two hands to put on or off the rope. Two commercial brands are Gibbs and Rock Exotica ascenders.
Both the toothed and ridged cam types use a concave working surface which engages the rope. Such a concave surface having teeth has the potential to exert a detrimental cutting force on a rope. The cutting force is simply the ratio of the weight divided by the area contacting the rope.
The present invention teaches a new, useful, and non-obvious set of crested curbs on the outside edges of the concave working surface on the cam face which engages the rope. Inside the concave surface are parallel flat ridges, each ridge having a flat top. The result is lower psi per contact point with the rope and additionally a higher total grip strength.
The ridges are uniquely positioned across the radius of the concave cam face to provide a superior grip without corresponding rope damage. The cams rounded curb margins uniquely prevent ropes from diagonal or unusual load/forces. In addition these cam crested curbs keep the rope geometrically aligned to prevent rope distortion torque and damage. Together the curb/ridges provide a higher grip at a lower PSI on the ropes.
Another advantage of the present invention is an integral safety lock which can lock the cam either open or closed. This lock can prevent accidental disengagement of a rope. This lock can also assist in the rapid and safe engagement should the user so choose.
The present invention can be used singly or in pairs. It can be mounted in rope ascenders, pulley safety locks, rope cleats or bits-marine, safety stops for workers on a rope, and fall protection devices.